Irrigation to Land

V2 DRAFT 4/06/2020

Discharge Option: Irrigation to Land

Description Location

Irrigation of treated wastewater to land provides an opportunity to not only utilise Irrigation of treated wastewater can occur to suitable land within a reasonable the wastewater as a water source and nutrient source for beneficial use on land conveyance distance from the wastewater treatment plant. Irrigation of treated but an opportunity to avoid, or reduce, the need for direct discharge of treated wastewater traditionally occurs on well to moderately well drained soils, on rural wastewater to surface water. Irrigation of treated wastewater to land, if managed type land. The soils need to be reasonably well drained to minimise the at appropriate levels, can also provide for further treatment of the wastewater, occurrence of saturated conditions or runoff. The irrigation site also needs to be reducing nutrients and pathogen migration to surface water. on land that is away from receptors and on land that can be maintained or developed into a land use in keeping with Wastewater irrigation can be conducted at varying Irrigation irrigation, such as pasture or trees. Assessment rates, depending on what the land use, soil type Topography is also a key consideration as Area and receiving environment, can manage. steep slopes can promote instability or Variations include: runoff of the wastewater. • Rapid infiltration (high rate). A GIS based assessment has been • Non-deficit irrigation (irrigating in excess of conducted to identify potentially suitable soil moisture requirements). irrigation locations within a 10 km radius of • Deficit irrigation (only irrigating when soil the wastewater treatment plant. moisture levels demand irrigation).

Irrigation Options Description Rapid infiltration This option would involve construction of a smaller footprint irrigation area over an area of highly permeable ground conditions. Topsoil layers are often removed and replaced with higher permeable gravels to improve infiltration rates. This option was considered previously in the Wainui Reserve and beach frontage (PDP 2001), however, it was considered that underlying geology may limit infiltration, requiring excessive infiltration areas. The existing wastewater treatment system may be suitable for this but with filtration also required. Non-deficit irrigation Non-deficit irrigation would involve irrigation to land at slow rates (several mm per day on average) when soil conditions allow. Irrigation (with seasonal storage) could occur when soil moisture levels are elevated (above field capacity) but not at risk of saturation. An indicative soil moisture model indicates that a non-deficit irrigation system at Raglan may require 110 ha to 140 ha of irrigable land but 150,000 m3 of partial storage would be required during extended wet weather periods (winter months, May to September). The existing wastewater treatment system would likely be suitable for this option. Close to deficit irrigation Deficit irrigation would incorporate irrigation of treated wastewater to land at slow rates (several mm per day on average) but generally (with seasonal storage) only when soil moisture levels demand irrigation (below field capacity). When irrigation is not achievable under this scenario, wastewater is stored in a lagoon (likely 300,000 m3 to 400,000 m3) and then irrigated when soil conditions allow. This option would likely require an active irrigation area of 300 ha to 550 ha. Irrigation would likely occur from October to April and storage would likely occur from May to September. The existing wastewater treatment system would likely be suitable for this option. Non-deficit irrigation with This non -deficit irrigation option would operate similar to the above non-deficit irrigation option, however, instead of storing treated alternative disposal location wastewater during elevated soil moisture conditions, treated wastewater could be discharged via an alternative pathway during wet soil V2 DRAFT 4/06/2020

conditions, such as one of the other disposal options. This would reduce the required irrigation area to 90 ha to 130 ha, with limited storage required (20,000 m3), to minimise discharge during summer storm events. Irrigation would primarily occur between October and April. The existing wastewater treatment system would likely be suitable for this option, depending on requirements of alternative discharge location. Deficit irrigation with This deficit irrigation option would operate similar to the above deficit irrigation option, however, instead of storing treated wastewater alternative disposal location during elevated soil moisture conditions, treated wastewater could be discharges via an alternative pathway, such as one of the other disposal options. This would reduce the required irrigation area to 240 ha to 280 ha, while still maintaining soil moisture levels below field capacity during irrigation periods. Limited storage (20,000 m3) would be required to minimise discharge during summer storm events. Irrigation would primarily occur between October and April when deficit conditions generally occur. The existing wastewater treatment system would likely be suitable for this option, depending on requirements of alternative discharge location. V2 DRAFT 4/06/2020

Options Assessment Criteria

Criteria Issue/Topic Description/Explanation Public Health Microbiological quality of treated Risk of public exposure to waterborne pathogens through: wastewater - Direct contact with the conveyance or treatment process - Direct contact with the receiving environment, for example through contact recreation - Indirect exposure, through food gathering (such as shellfish, fish, watercress, etc) and groundwater use. Health effects from irrigation Risk of public exposure to pathogens from irrigation. Treated wastewater re-use Risk of contamination from treated water for non-potable re-use. Environment Water quality Potential effects on freshwater (surface and ground) and coastal/marine receiving environments Aquatic ecology Potential effects on aquatic ecosystems Terrestrial ecology Potential effects on terrestrial ecosystems and soils Coastal environment and resources Potential effects on significant coastal and marine areas, existing harbour and coastal processes, and physical footprint within the harbour and coastal marine area. Cultural Mauri Potential effects on mauri of land, water and air Kai moana Potential effects on kai moana and the kaitiaki management of customary fishing Cultural values Potential effects on the relationship of Maori and their culture and traditions with their ancestral lands, water, sites, waahi tapu and other taonga Health and Wellbeing Potential effects on the ability of the land, sea and air to support wairua in order to maintain health and wellbeing for Maori Social and community Amenity value and aesthetics Potential effects on the natural and built environment (e.g. visual, odour, noise) Urban development Extent to which the option enables residential and commercial development within the projected timeframe Recreation Extent to which the project enhances or detracts from local recreational activities and opportunities Food gathering Extent to which the project enhances or detracts from people’s ability to collect food within the area Access to the coast Extent to which an option effects access to the coastal marine area. Re-use potential of option Extent that treatment by-products can be utilised beneficially now and into the future (i.e. irrigation/nutrients for food production) Sustainability Carbon footprint Potential embodied and operational carbon footprint Constructability Geology, soil, groundwater conditions Option suited to local environmental conditions Land availability, accessibility Adequate and secure land must be available for the required infrastructure, timescales that fit within project timing Existing infrastructure Potential to maximise use of existing infrastructure that has a valuable remaining economic life, e.g. power supply, treatment plants, pumps, conveyance pipes and existing sites. Technology Reliable, proven and robust technology To be sustainable, an option should be based on proven technology and have adequate redundancy (spare operational capacity to provide back-up in case of failure) Adaptable and flexible Due to the uncertainty associated with future growth, a feasible option must be able to adapt to changing conditions such as increased flows and loads, discharge quality requirements, input requirements, and energy availability. Able to be staged The extent to which an option could be staged (e.g. through modularised components). Operational and engineering resilience The option must be sufficiently resilient to natural hazards and operational failure. Financial Implications Capital cost Is the cost of the project appropriate for the project area and the population served? Operating and maintenance cost Can the capital infrastructure be maintained and operated in a cost-effective manner? Whole of life cost How do the whole of life costs pf the various options compare? Financial risk Is the option affordable even if growth does not occur as predicted? Opportunities and Benefits Opportunity for resource recovery The provision of beneficial reuse of treated wastewater. (i.e. with emphasis on food production) The potential for beneficial reuse of biosolids. (i.e. with emphasis on food production) Statutory Policy Considerations Consistency of the option with National Includes consistency with the New Zealand National Coastal Policy Statement (NZCPS), National Policy Statement Policy Statements (NPS) for Freshwater Management (NPS-FM) and any other relevant NPS V2 DRAFT 4/06/2020

Consistency of the option with any other Includes consistency with the Reserves Act, and any other relevant Act relevant legislation outside of the Resource Management Act V2 DRAFT 4/06/2020

Options Assessment

Land treatment options are assessed based on the above criteria in the following table. Key: Red – Largely fails to meet the criteria, Amber - Marginally meets the criteria, Green - Meets criteria well Irrigation Public Environment Cultural Social & Sustainability Constructability Technology Financial Opportunities Statutory Comments Carry Option Health Community Implications and Benefits Policy forward Considerations to short list? Rapid Can be May result Hapū have No direct Will likely Unlikely to be Not a Likely high Potential site Potential for Not carried No Infiltration isolated in excessive reiterated discharge to require feasibly suitable cost due to at Wainui discharge to forward due from public groundwater opposition to surface excessive constructed technology excessive Reserve coastal waters to geological and spray mounding/ marine options water but disposal bed given previous for the earthworks close to if located in limitations irrigation break out and support for risk of and assessments location WWTP proximity to can be re-use options. groundwater associated (PDP 2001) the coast. avoided Avoidance of mounding earthworks 11m3/d/100m Policy adverse public may cause resulting in a 23(2)(b)(ii) of health and community larger carbon the New environmental concern footprint. Zealand effects obviously Coastal Policy aligns with hapū Statement ethics. Any option 2010 (NZCPS) with elevated risk has relevance wouldn’t be -see notes supported Non- Risk of Potential to Hapū have Generally Generally Moderate land Common Land Beneficial Potential for Carried Yes deficit spray drift promote reiterated well thought sustainable requirement Technology. purchase Reuse adverse forward due irrigation but nutrient opposition to of but land but need to and may be Treatment: may be high effects on to smaller (with disinfection migration marine options purchase be careful challenges in Pond cost. freshwater land area seasonal and buffer but can be and support for and not to obtaining system and Irrigation quality as a (compared storage) distances managed re-use options. opposition displace key access and UV construction result of with other will with Avoidance of from food pipeline route. and pipeline nutrient land mitigate appropriate adverse public neighbours production costs migration. treatment this land use health and may be land. moderate. Further work options) while environmental challenging Potential Large storage required to not requiring effects obviously carbon sink if volume cost assess a seasonal aligns with hapū trees utilised. may be high. consistency alternative ethics. Any option with the disposal with elevated risk National Policy options. wouldn’t be Statement for supported Freshwater Management 2014 (NPS- FM).

Given groundwater discharge will potentially flow V2 DRAFT 4/06/2020

Key: Red – Largely fails to meet the criteria, Amber - Marginally meets the criteria, Green - Meets criteria well Irrigation Public Environment Cultural Social & Sustainability Constructability Technology Financial Opportunities Statutory Comments Carry Option Health Community Implications and Benefits Policy forward Considerations to short list? to the coastal environment, . Policy 23(2)(b)(ii) of the New Zealand Coastal Policy Statement 2010 (NZCPS) has relevance -see notes Close to Risk of Nutrient Hapū have Generally Generally Large land Common Very high Beneficial Potential for Not carried No deficit spray drift migration reiterated well thought sustainable requirement Technology. cost: Land Reuse adverse forward due irrigation but reduced, opposition to of but land but need to and may be Treatment: purchase effects on to large land (with disinfection less risk of marine options purchase be careful challenges in Pond may be high freshwater area seasonal and buffer runoff and support for and not to obtaining system and cost. quality as a requirements. storage) distances re-use options. opposition displace key access and UV Irrigation result of will Avoidance of from food pipeline route. construction, nutrient mitigate adverse public neighbours production pipeline and migration this health and may be land. storage costs (although environmental challenging Potential moderate. lower than effects obviously carbon sink if Large storage non-deficit aligns with hapū trees utilised volume cost irrigation). ethics. Any option may be high. Further work with elevated risk required to wouldn’t be assess supported consistency with the NPS- FM.

Given groundwater discharge will potentially flow to the coastal environment, . Policy 23(2)(b)(ii) of the New Zealand Coastal Policy Statement 2010 (NZCPS) has relevance -see notes V2 DRAFT 4/06/2020

Non- Risk of Potential to Hapū have Generally Generally Smaller land Common Land Beneficial Potential for Carried TBD deficit spray drift promote reiterated well thought sustainable requirement Technology. purchase Reuse adverse forward due irrigation but nutrient opposition to of but land but need to but may be Treatment: may be effects on to smaller with disinfection migration marine options purchase be careful challenges in Depends on moderate freshwater land area alternative and buffer but can be (i.e. potentially an and not to obtaining alternative cost. quality as a (compared disposal distances managed ‘alternative opposition displace key access and discharge Irrigation result of with other method will with disposal method’) from food pipeline route. construction nutrient land (either mitigate appropriate and support for neighbours production and pipeline migration. treatment marine this land use re-use options. may be land. costs Further work options). outfall or Avoidance of challenging Potential moderate. required to Feasibility DBI adverse public carbon sink if Costs of assess depends on during wet health and trees utilised supporting consistency availability of winter environmental disposal with the NPS- suitable months- effects obviously pathway FM. seasonal see aligns with hapū needs alternative notes) ethics. Any option consideration. Other effects disposal with elevated risk dependent on options. This wouldn’t be alternative will supported. disposal realistically Greater location, be limited to understanding on however given marine outfall the alternative groundwater or DBI. (see disposal method discharge will notes on DBI) would be required potentially flow to the coastal environment, . Policy 23(2)(b)(ii) of the New Zealand Coastal Policy Statement 2010 (NZCPS) has relevance -see notes Close to Risk of Nutrient Hapū have Generally Generally Moderate land Common Very high Beneficial Potential for Not carried No deficit spray drift migration reiterated well thought sustainable requirement Technology. cost. Land Reuse adverse forward due irrigation but reduced, opposition to of but land but need to and may be Depends on purchase effects on to large land with disinfection less risk of marine options purchase be careful challenges in alternative may be high freshwater area alternative and buffer runoff. (i.e. potentially an and not to obtaining discharge cost. quality as a requirements. disposal distances Supporting ‘alternative opposition displace key access and Irrigation result of method will seasonal disposal method’) from food pipeline route. construction nutrient (either disposal neighbours production and pipeline migration V2 DRAFT 4/06/2020

Key: Red – Largely fails to meet the criteria, Amber - Marginally meets the criteria, Green - Meets criteria well Irrigation Public Environment Cultural Social & Sustainability Constructability Technology Financial Opportunities Statutory Comments Carry Option Health Community Implications and Benefits Policy forward Considerations to short list? marine mitigate method and support for may be land. costs (although outfall or this needs to be re-use options. challenging Potential moderate. lower than DBI included. Avoidance of carbon sink if Costs of non-deficit during wet adverse public trees utilised supporting irrigation). winter health and disposal Further work months- environmental pathway required to see effects obviously needs assess notes) aligns with hapū consideration. consistency ethics. Any option with the NPS- with elevated risk FM. wouldn’t be supported. Other effects Greater dependent on understanding on alternative the alternative disposal disposal method location, would be required however given groundwater discharge will potentially flow to the coastal environment, . Policy 23(2)(b)(ii) of the New Zealand Coastal Policy Statement 2010 (NZCPS) has relevance -see notes

V2 DRAFT 4/06/2020

Notes

Either Option dismissed after ELT review

Scenario 1 (If DBI is to be completely dismissed) DBI has been dismissed as a primary option for full discharge of treated wastewater, given: • a strong community and hapū view toward land/re-use option investigation discharge options.

DBI has also been dismissed as a potential ‘alternative disposal method’ during winter months

Option to be retained after ELT review

Scenario 3 (If DBI is to be retained fully after WDC consideration) No short list wording would be needed

Scenario 2 (If DBI is to be costed only, with no feasibility testing undertaken- refinement toward a BPO couldn’t occur without bore testing DBI has been dismissed as a primary option for full discharge of treated wastewater, given: • a strong community and hapū view toward land/re-use option investigation discharge options. Inclusion within the short list as a supplement to non-deficit (summer) irrigation allows for a potential re-visit with the community and hapu, should feasibility of preferred options be ruled out. It is recognised that other disposal options have closer alignment to the consenting project objectives, where investigative priority is to sit with these. Given that DBI is however a non-marine disposal, it is practical to include the option for DBI costing only for contingency planning. Any progression would need additional engagement between WDC/ hapū and community. A test bore would have been appropriate to establish DBI feasibility if greater favour had been offered. - In reference to Policy 23(2)(b)(ii) of the New Zealand Coastal Policy Statement 2010 (NZCPS), a clear understanding from Raglan tangata whenua after engagement is that the present treated wastewater marine discharge is offensive to their values, with a substantial adverse effect resulting. Any alternative discharge method that enables satisfactory whenua contact and re-use potential, should have in principle support.